Percentages of mature male and female vermilion snapper, Rhomboplites aurorubens, based on total length (TL) and age were calculated for five three-year periods during 1979-93. Males and females collected during 1982-87 became sexually mature at a smaller size and younger age than individuals collected during 1979-81. The median TL at maturity for females decreased from 160 mm in 1979-81 to 151 mm in 1985-87. The median TL at maturity for males was 145 mm during 1979-81. During 1985-87 all males were mature at 140 mm. The temporal shift toward a smaller size at maturity was more pronounced in males than in females. The percentage of mature males at age 1 significantly increased from 63.6% in 1979-81 to 100% in 1985-87 and afterwards. More than twice as many females at age 1 were mature in 1985--87 (48.6%) as in 1979-81. The decline in size and age at maturity may have been caused by fishing pressure that gradually increased during the 1980's. The sex ratio of vermilion snapper was dependent upon latitude and gear type but was generally independent of water depth, fish length, and sampling years. Although the sex ratios were significantly different among latitudes, there were no trends among latitudes 31°N, 32°N, and 33°N. The percentage off males was 72.1%,68.0%, and 59.9% for vermilion snapper caught by trap, hook-and-line, and trawl, respectively. Reasons for the difference in sex ratio among gear types are unclear, suggesting that caution must be used when interpreting sex ratios estimated for any fish species collected by various gear types.